Determining dwelling unit count at an address using 1950 Census records

March 11, 2023 / / 0 Comments

It’s possible to use 1950 U.S. Census records to establish a number of historic dwelling units at a building in Chicago for the purposes of the city generating a “zoning certificate”. That’s a recognition of the number of legal dwelling units especially useful when that number of dwelling units is greater than the current zoning code allows. They’re required to be generated (i.e. requested from the city’s planning department) during the sale of a small-scale residential property.

This Chicago zoning certificate was generated the “normal” way (which I don’t know how to describe), while this blog post is about digging up evidence in case the normal way doesn’t affirm the number of dwelling units you want it to affirm.

However, based on a recent experience of a client of mine, the zoning certificate – while supposedly valid for one year – is subject to dispute later! Finding Census records showing the same or more dwelling units in a given building has helped re-establish the validity of the number of units stated in a zoning certificate.

It will take you some time to research Census records! (I would budget at least one hour. There is a painstaking process to find the webpage that has the enumeration (counting) sheets for the address you want, and it will take some time to sift through those sheets (and you may have to look at multiple pages for the same address).

Here are the steps involved

  1. Find the enumeration district (ED).
  2. Go to that ED’s set of sheets in the National Archives 1950 Census website.
  3. Page through and read every sheet until the address is found.

Find the enumeration district

The New York Public Library has a great tutorial on their blog, and I recommend you start by reading section 2, Generate an ED number.

Once you locate the ED (following the instructions in Section 2) I would say stop reading the NYPL blog post.

Alternatively, for Chicago address lookups, you can browse these maps of the enumeration districts and then search for those ED numbers directly on the National Archives website.

Section 2 will advise you to use Steve Morse’s third-party Unified Census ED Finder (which is the most useful part of this process). The ED Finder has a wizard asking you to select state, county, city, and street name and cross street. It will then produce a set of one or more ED numbers under the heading, “1950 ED numbers corresponding to your location”.

A screenshot of the ED Finder “wizard”.

Tip: ED Finder will likely show you multiple ED numbers; you may need to look at all of them to find an address. I think this happens because the link between each enumeration district and a city’s streets is imprecise

Click each ED number, which opens a new tab in the ED Finder website with links to three different image viewers. These are databases where scans of microfilm are shown online. One of them, NARA, is public – that’s the National Archives & Records Administration. I recommend that one as it’s free and doesn’t require an account.

Read each enumeration sheet

Once you arrive on the NARA website click on the “Population Schedules” to reveal the enumeration sheets. Start paging and reading!

Tip: Street names are written vertically on the left edge of the page.

A screenshot of the 1950 Census database and website of NARA. It’s necessary to click the “population schedules” button to display the enumeration sheets.

The NARA viewer isn’t the best – it doesn’t allow you to make it full-screen; I was constantly having to zoom in to read the street names and house numbers.

A screenshot of a 1950 Census enumeration sheet with two annotations.

Creating a PostgreSQL PostGIS function to get around a DataTables Editor limitation

March 8, 2023 / / 0 Comments

DataTables is a fantastic software that turns any HTML table into an interactive and editable one.

Chicago Cityscape uses DataTables on pretty much every page. DataTables also provides server-side processing for PHP to grab the right data from a database and show it to the user, 10 records at a time (the number of records can be changed by the user to show more records at a time).

Screenshot showing my new function, using the function, and the results.

Problem

One of the problems I’ve had to get around is that the DataTables Editor script recognizes a SELECT statement with only one function per field. If there’s a second function that’s manipulating a field in the SELECT statement then the ALIAS won’t work and the JavaScript will not be able to read and show the data properly.

I almost always use the two functions ST_AsGeoJSON and ST_Transform on my geographic data to (1) transform it from the SRID of 3435 to 4326 for displaying on web mercator maps, and (2) converting the GIS data into GeoJSON strings for easy transference to the Leaflet JavaScript library.

This is a known issue – see this thread on the DataTables forums – that Allan, the DataTables creator, has acknowledged and provided an alternative solution for.

Solution

It turns out that it’s easy to write a function that combines both functions. 

CREATE OR REPLACE FUNCTION ST_TransformAsGeoJSON (field geometry, srid int =4326, simplify int =5)
  RETURNS text
RETURN ST_AsGeoJSON(ST_Transform(field, srid), simplify);

The code above is a function I call ST_TransformAsGeoJSON that combines the two functions I already described, and is flexible by letting the user specify in the arguments the table and field, the SRID to transform (reproject) to, and the simplify variable that can be used in ST_AsGeoJSON that tells it how many decimal points to use in coordinates.

Avoid “VARCHAR” columns in PostgreSQL [PGSQL Phriday #006]

February 28, 2023 / / 1 Comment

This is a response to Grant.

This is one thing I wish I knew while learning PostgreSQL: Don’t ever use the VARCHAR column type. I have never encountered a situation where that would have been superior to using TEXT.

The problem with VARCHAR column type is that it can be a fixed-width column that doesn’t allow text longer than a certain number of characters. This maximum character length can be introduced by the person who creates the table and adds the column.

The maximum character length can also be created by a GIS program (specifically, QGIS and the ogr2ogr command line tool) as well as some online tools that can convert spreadsheets to SQL and even write the table definition and “CREATE TABLE” statement. In both cases, the program tried to guess the column type and seemed to default to VARCHAR(y character length) instead of TEXT.

The maximum character length is a problem because trying to insert more text than allowed into that field will encounter an error and the INSERT or UPDATE statement will fail. I think it’s also a bad idea to create these columns because it makes it expensive to change your mind later about what length of text will go into that field.

Other things I wish I knew earlier

  • Using transactions to test your query and its affect on your data so that you can easily undo any changes.
  • How and when to use indexes beyond the “btree” index type (for example, “gin” for array and JSONB columns).
  • Add “time_created_at” and “time_updated_at” columns to basically every dataset. This makes it easy to sort things later; sometimes when creating a new dataset it’s not always obvious how you might want to display or manipulate the data until days, weeks, or months later. Sorting data by “when was the information changed last” is a common use case for me.

Two-flat journal 8: Adding a third unit

February 17, 2023 / / 0 Comments

Over the years I waffled once or twice about adding a third unit, in the basement. I hired a structural engineer to draw up plans for the replacement center beam in the basement’s ceiling. To “future proof” the plans, I also asked him to draw a plan and create specifications for a floor excavation in order to achieve a code-compliant ceiling height in the potential basement unit.

The basement, looking towards the front entry. Notice how smooth the floor is.

The waffling was based on the cost of the necessary digging down. Excavation will add about $25,000 to the cost of the project. (That’s based on one bid, the only bid that called it out specifically. I asked all three bidders to separate the costs of the basement unit so that I would know exactly how much the basement unit – excavation, walls, finishes, etc. – would cost as an “add on”.)

I think my architect also helped convince me to design and get bids for a third unit because of the flexibility it could provide for me and my tenants (which may include one or more family members), as well as the possibility of additional rental income.

I’ve settled on adding the third unit, and I’m excited to do it, in part because of my well-known enthusiasm for accessory dwelling units. (A note about Chicago’s ADU ordinance: this property is outside the ADU pilot area but it has unused zoning capacity per both the FAR and minimum lot area per unit standards so the additional unit is allowed without the ADU ordinance.)

Excavation

The Chicago Building Code requires that the ceiling height be a minimum of 7′-6″ in most of any dwelling unit (that’s measured from the finished floor to the finished ceiling). A limited amount of area is allowed to be lower to get around existing or newly installed pipes and ducts in the ceiling.

To achieve that, crews will demolish and remove the existing floor slab (which I’ll be a little sad about because the previous owner did a nice job pouring it) and excavating earth 10″ down. They’ll also underpin the foundation walls in an alternating pattern of rectangles around the perimeter. I hope I can explain underpinning well (otherwise watch Darren Voros’s video): This means they’ll dig under half of the foundation dispersed around the perimeter (the A sections), leaving unexcavated space between each to hold up the other half of the foundation (the B sections); then they’ll switch and repeat the process for the B sections.

A foundation wall detail showing the 10″ of excavation and the addition of a perimeter drain tile.

Water

After every rain storm I go and check the house. The basement has been dry every time. I’m surprised, and thankful, that it seems that water doesn’t seep into the basement.

One time I noticed that there was water pooling on the basement floor – when a rain storm had not occurred. It turned out that when I closed the water service line I didn’t close it well enough and water was very slowly leaking out. Tightening the valve handle was a simple resolution.

During the excavation there will be a perimeter drain tile system installed under the floor slab to steer water toward an ejector pit. An ejector pit is different than a sump pump in that it has a mechanism to grind the house’s sewage before pumping it to the city’s sewer main. I believe an ejector pit is a requirement when the lowest dwelling unit’s plumbing (i.e. the toilet) will be below the city sewer main.

Bob Vila’s website describes interior drains like this:

Similar to exterior drain tile, an interior French drain features a perforated pipe that carries water to a collection pit where it can be pumped to the surface. This type of drain is located along the interior perimeter of the basement and lies below floor level.

All You Need to Know About Basement Drains, Glenda Taylor and Bob Vila

Apartment

The new dwelling unit is drawn as a 1-bedroom apartment with a small bedroom that has two short windows and a closet. It has a large, combined living room, dining room, and kitchen.

The entryway is partially separated from the big room using a hall closet, creating a sort of mud hall. The bathroom is of a typical size for small apartments in Chicago and there’s a considerably sized utility room for laundry and storage. Overall, the apartment has an area of about 720 s.f.

I believe in-unit storage to be an important amenity. My current apartment is a studio and I selected it in part because it had good layout with a lot of scattered storage (there’s a walk-in closet, a large nook between the living area and the bathroom, a small closet, and a linen closet in the bathroom).

When I was looking for a new place to live in 2022 I didn’t want to have to move any of my stuff into a storage locker in the building or a storage unit in another building.

Other space in the basement

The rest of the basement, about 100 s.f., will have two hybrid heat pump water heaters, the ejector pit, electrical panels, and a little bit of room for storage. There’s also a rear entryway and the basement apartment will have a rear exit through here.

A short list of features of the Netherlands that I still try to wrap my head around

January 18, 2023 / / 0 Comments

The Netherlands is the country I’ve visited the most, going there eight times between 2011 and 2022. I’ve obsessively visited 31 cities, the Hoge Veluwe national park, and plenty of other places outside cities.

Here are three land use and infrastructure characteristics that continue to fascinate me.

Transportation systems, obviously

Learning about how the Dutch created the safest network of streets for cycling is what started my near-obsession 15 years ago.

Then I went there in 2011 and I got to experience it for myself (photos from that trip).

I think the quality, capacity, likability, and integration of their transportation systems can be summarized best, for Americans who haven’t been there, by learning the results of a Waze survey: People who primarily drive in the Netherlands are more satisfied with the driving in their country than people in other countries are with driving in theirs.

In other words…if you like driving, then you should also care about what the Netherlands because they happened to also create the most driver-friendly transportation system.

Creating land & living with flooded land

As a novice, it’s probably easier to notice and understand how the Dutch create, move, and live with flooded land from above. There have been moments while I was cycling in the country where I’ve ridden past “polders” and former lakes and seas only to realize it later that I had biked through a massively transformed area that appeared entirely natural.

When I lived in Rotterdam for three months in 2016 I tried to visit as many places across the country as I could. I especially wanted to visit Flevopolder, the larger part of the Flevoland province, built from of the sea in 1986 where 317,000 people live.

I visited both major cities on the Flevopolder in the same day, Almere and Lelystad, the capital. I cycled from Almere (photos) to the seafront of Markermeer, and…get this…had to ride uphill because the land is below sea level.

Reaching the edge of Flevopolder, where it borders the sea called Markermeer
Cycling uphill to meet the sea north of the city of Almere, in the Flevoland province of the Netherlands.

Most Dutchies live below sea level, and the country has massive land and metal engineering works to keep the water in check.

The Dutch, especially in and around Rotterdam, come up with new ways to deal with water and export this knowledge abroad.

While the existing and planned measures should be sufficient until at least 2070, too much uncertainty over the progress of climate change remains afterwards to assess whether the city will truly stay liveable.

Some assessments suggest that if the sea rises by 5m – an estimate in sight within a century, considering the unpredictability of the rate that Greenland and Antarctica’s glacier will melt – Rotterdam will have no other choice but to relocate.

“Rotterdam: A bastion against rising sea, for now”
By Zuza Nazaruk

The country may rely on electricity to survive more than most: it’s needed to keep the pumps working, to keep the water in the sea instead of in and over the land.

How productive their agriculture industry is

By land area, the Netherlands is a very small country; it would be the tenth smallest state in the United States. By population, it would be the fifth largest state (17.6 million, greater than Pennsylvania’s 13 million).

Given that, how is it that the Netherlands is the world’s second largest exporter of agricultural products by value, after the United States?

Simple answer: High-quality, high-value, high-demand foodstuffs; space-efficient farming practices, including a significant amount of food grown vertically and in greenhouses. And, I don’t remember if this was in the article, very good transport connections to trading partners through seaports, canals, railways, and motorways.

I was surprised to see that both brands of canned cold brew coffee sold at the convenience store in my apartment building are produced in the Netherlands.